The actor, best known for his stint on "Saturday Night Live," was involved in a crash earlier this year on a Los Angeles freeway when his Mercedes Benz collided with a parked vehicle, reports TMZ. At the time, Kattan was taking the prescription sleep drug Ambien.

How do prescription drug DUI charges work?

Driving Under the Influence of Drugs

DUI charges for driving under the influence of drugs are generally treated much the same as DUI charges involving alcohol. The major difference between the two, however, is the ability of police to measure impairment.

For an alcohol DUI, police can measure a driver's blood alcohol concentration using a Breathalyzer device or blood test and compare it to the legal limit, generally 0.08 percent. For drug DUI, however, measuring impairment is far more subjective.

Police generally must rely on observations made during field sobriety tests, which allow an officer to observe a suspected DUI driver's balance, physical ability, attention level, and other factors that the officer then uses to determine whether the suspect is impaired. The presence of drugs can be confirmed using blood tests, although the presence of drugs in a suspect's blood stream may not be itself determinative of impairment for purposes of DUI.

Prescription Drugs Are No Exception

A drug prescribed by a doctor can be just as likely to get a driver busted for drugged-driving DUI as an illicit narcotic. In Kattan's case, it was the sleep aid Ambien, which can leave drivers impaired for hours after being taken and in some cases can lead to "sleep driving," in which drivers operate their vehicles with later having no memory of having done so.

Other common prescription medicines that can lead to DUI charges include: antidepressants, decongestants, pain killers, antihistamines, and tranquilizers such as Valium.